I'm willing to start a new project using PlantUML but at the point of download src/jar I saw many downloads with different licences. I also search Q&A to see old questions on the same topic and red faq.html .
It seems that there are some differences about features between GPL version and other versions, for example PSystemTuringFactory.java is not present into the MIT version.
I did not get the point of this licence scheme: usualy one uses GPL to force a strong copyleft on its work, instead publish a version under the MIT license does not require this copyleft and allow closed source applications. So GPL seems redundant.
Also LGPL is point less for the same reason. EPL could have a reason with double licensing only GPL and EPL because they are incompatible. But with MIT I don't get the point either.
So my qustions are:
why the licensing scheme instead of only the MIT license?
features difference between GPL (it's the full version?) and the other versions?